A related-art image forming apparatus is configured to: expose an electrically-charged photoconductive drum to light; forms an electrostatic latent image on the photoconductive drum by changing the electric potential of an exposed area; and transfer to a recording sheet a developer image formed by supplying developer to the electrostatic latent image, thereby recording a predetermined image on the recording sheet.
JP-A-9-160333 describes an image forming apparatus including: a plurality of LED heads (exposure members) configured to radiate light on a plurality of photoconductive drums; and a plurality of process units, each of which includes a photoconductive drum and a toner accommodating chamber, wherein the LED heads and the processes units are alternately arranged in a longitudinal direction. In the image forming apparatus, the LED heads are supported by rotatable top cover and configured to move to and away from the photoconductive drums in association with the rotation of the top cover. A rotation axis of the top cover is rotatably fixed to a rear side portion of an apparatus main body relative to each of the process units, whereby each of the LED heads moves from the front side to the rear side between an exposure position where the photoconductive drum can be exposed and a retracted position where the LED head is retracted from the process unit. Further, the rotation axis of the top cover is situated at substantially the same position (hereinafter called a “head position”) of each of the LED heads situated at the exposure position with respect to the vertical direction. Therefore, a tangential line of a locus of the rotation movement of each of the LED heads at the exposure position is oriented substantially upwardly. Accordingly, the respective LED heads are retracted from spaces among the respective process units in a substantially upward direction.
However, in the image forming apparatus, the locus of rotation movement of the LED head assumes the shape of a circular arc. Hence, clearance between the process units is set to a certain size such that the respective LED heads do not interfere with the respective process units. In particular, when the rotation axis of the top cover is set at a position higher than each of the head positions, a tangential line at the exposure position of the locus of rotation movement of each of the LED heads tilts in an obliquely upward direction toward the front, so that the locus of rotation movement of each of the LED heads bulges to the front. Therefore, it is necessary to set the gap between the process units greater. When the rotation axis of the top cover is situated below the head position, a tangential line of the locus of rotation movement of each of the LED heads at the exposure position tilts in an obliquely upward direction toward the rear side, and the rotation locus of the LED head tilts toward the rear side. Therefore, it is necessary to set a gap among the respective process units greater.